Method of producing acid fluorides from acid chlorides

ABSTRACT

Acid fluorides, for example carboxylic acid fluorides and sulfuryl fluoride are produced by reacting the corresponding acid chlorides with hydrogen fluoride adducts of ammonium fluoride or amine hydrofluorides (which act as a catalyst or as a fluorination agent). Consumed HF adducts may be regenerated with HF.

The invention relates to a method of producing acid fluorides from acidchlorides by contacting with hydrogen fluoride adducts of nitrogen-basehydrofluorides.

Acid fluorides, for example carboxylic acid fluorides and sulphurylfluoride, are advantageous products for use per se or as intermediateproducts. Sulphuryl fluoride, for example, can be used as a fumigant forvermin, e.g. in wood used in buildings, churches, museums, silos andbuildings, and to counteract discolouring enzymes, fungi or pathogens inwood which has not been used for building, e.g. freshly felled wood.Carboxylic acid fluorides are valuable intermediate products in chemicalsynthesis. Sulphuryl chloride fluoride can be reacted to form sulphurylfluoride.

German Offenlegungsschrift DE-OS 28 23 969 discloses the preparation offluorocarbonyl compounds from chlorocarbonyl compounds, for example ofchlorodifluoroacetyl fluoride from chlorodifluoroacetyl chloride and HFadducts of hydrofluorides of organic nitrogen bases as fluorinationagents. If HF adducts are used, amine is added to bind HF, or solventshaving sufficient alkalinity are used to bind HF.

It was an object of the present invention to devise an improvedfluorination process for the preparation of acid fluorides from acidchlorides. This object is achieved by the method of the presentinvention.

The method according to the invention provides for acid fluorides to beprepared from acid chlorides by contacting with hydrogen fluorideadducts of hydrofluorides of organic nitrogen bases or ammoniumfluoride. In this case, the method is carried out so that, unlike in theprior art, no base which has an HF-binding effect is added. Nor is anysolvent which binds HF used. At best, if in accordance with anembodiment to be described hereafter an acid is added, such astrifluoroacetic acid, this acid or part of this acid may be neutralisedby base, by adding a desired quantity of base before, during or afterthe addition of acid. However, HF is not bound.

In addition to HF adducts of ammonium fluoride, the HF adducts ofhydrofluorides of organic nitrogen bases named in GermanOffenlegungsschrift DE-OS 28 23 969 can be used for contacting. They canbe expressed by the formula B.(HF)_(x), wherein B represents an organicnitrogen base and x is a whole number or a fraction from <1 to 4,preferably 2-3.

Any possible primary, secondary and/or tertiary amines includingN-heterocycles may be used as organic nitrogen bases B. If these aminesare represented by the formula:

R ₁ R ₂ R ₃ N

the meanings therein could be as follows:

R₁ an alkyl radical, preferably having 1 to 10, in particular 1 to 6, Catoms, a cycloalkyl radical, preferably having 5 to 7 C atoms, anaralkyl radical, preferably having 6 to 10 C atoms, or an aryl radical,preferably likewise having 6 to 10 C atoms; R₂ and R₃ hydrogen, alkyl,cycloalkyl, aralkyl and aryl radicals of the same type as stated underR₁.

The radicals R₂ and R₃ may be identical or different. Two of theradicals R₁ and R₂ or R₃ may also be closed to form a cycloaliphaticring, which may optionally be interrupted by other heteroatoms such asoxygen atoms. Likewise, it is possible for the three radicals R₁, R₂ andR₃ to be constituents of a heterocyclic ring, which means thatcorresponding N-heterocycles then result. Preferred organic nitrogenbases B are primary, secondary and/or tertiary amines having a total ofup to 12 C atoms, the secondary and/or tertiary aliphatic amines beingparticularly preferred.

Concrete examples of the bases B are:

N-butylamine, N-decylamine, diethylamine, di-n-octylamine,trimethylamine, triethylamine, tri-n-propylamine, isopropyldiethylamine, tri-n-butylamine, cyclohexylamine, N-methylaniline,N,N-dimethylaniline, pyrrolidine, piperidine, N-methylpiperidine,morpholine, pyridine, quinoline, etc.

The HF adducts of the hydrofluorides of the nitrogen bases B can easilybe obtained from the bases B and hydrogen fluoride; they are low-meltingsubstances, or substances which are liquid at room temperature, withconsiderable thermal loading ability. The tris-hydrofluorides can evenbe vacuum-distilled in non-decomposed form.

Preferably HF adducts of primary, secondary or tertiary aminehydrofluorides having up to 15 C atoms are used, in particular secondaryand tertiary amine hydrofluorides. HF adducts of tri-n-propylaminehydrofluoride, tri-iso-propylamine hydrofluoride, tri-n-butylaminehydrofluoride, pyridine hydrofluoride, piperidine hydrofluoride orN,N-dimethylamine hydrofluoride are particularly well suited.

The reaction is performed in liquid phase.

The method according to the invention may be performed batchwise orcontinuously. In the continuous procedure, the procedure may consist ofalso feeding in HF, fresh HF adduct or both in addition to the acidchloride to be fluorinated. Correspondingly, reaction mixture isseparated off or gaseous reaction products are distilled off or removedin gaseous form.

The inventors have discovered that HCl becomes enriched in the reactionmixture over time. If HF is not fed in intermittently or continuously,the reaction mixture or the HF adduct becomes depleted in HF. It hasbeen discovered that the HF adduct can be regenerated by treating withHF, optionally at elevated temperature (80 to 120° C.) and elevatedpressure (e.g. autogenous pressure in an autoclave). In so doing, it wasshown that it is not necessary completely to expel any HCl present. Aresidual content of e.g. less than 5% by weight, preferably less than 2%by weight, HCl is acceptable.

According to one embodiment of the invention, sulphuryl fluoride as acidfluoride is prepared from sulphuryl chloride or sulphur dioxide andchlorine (then under pressure for liquefaction). Here, in order torelease HCl, an acid is added, for example a halogenated carboxylic acidsuch as trifluoroacetic acid. A nitrogen base may be added for (partial)neutralisation of this added acid. In that case, this base expedientlycorresponds to the base contained in the hydrofluoride.

Sulphuryl fluoride may also be prepared from sulphuryl chloridefluoride. Thus two-stage preparation of sulphuryl fluoride is possible.The first stage comprises the preparation of sulphuryl chloride fluoridefrom sulphuryl chloride. The ratio of amine (or NH₃) to HF in thereaction mixture is not limited in this stage; it can also be performedwith a very high HF content, e.g. at a ratio of amine to HF of 1:3 up to1:10 or even above. The second stage, the fluorination of sulphurylchloride fluoride to sulphuryl fluoride, requires a ratio of amine to HFwhich is greater than 1:3; for example, it is between 1:2 and 1:3. Thisproviso in terms of the maximum content of HF in the reaction mixturealso applies to one-stage preparation of SO₂F₂ from SO₂Cl₂, if a goodyield of SO₂F₂ is to be obtained. It is assumed that for a ratio ofamine to HF of less than 1:3 the reactivity (nucleophilic character) ofthe F⁻anion changes.

The two-stage preparation of sulphuryl fluoride makes it possible to usea particular method variant, because it has been established that it issimultaneously possible to regenerate the HF adduct (as mentioned above)during the fluorination of SO₂Cl₂ to SO₂ClF. SO₂Cl₂, an excess of HF andHF adduct which is to be regenerated are introduced into a reactor. Atelevated pressure (e.g. autogenous pressure in an autoclave), SO₂ClF andregenerated HF adduct are produced simultaneously. Gaseous HCl whichforms is separated off (e.g. by letting off the superatmosphericpressure and passing though inert gas such as N₂). Then HF is evaporatedoff, in order to bring the HF content to within the limits describedabove (amine : HF>1:3). Then the second stage can be performed for thepreparation of SO₂F₂. If the first and second stages are performed inthe same reactor, it is thus possible always to enter the second stagewith re-fluorinated HF adduct.

According to another embodiment, carboxylic acid fluorides of Formula I

 RC(O)F

are prepared in which R stands for C1-C7-alkyl; or for C1-C7-alkylsubstituted by at least 1 chlorine atom and/or by at least 1 fluorineatom. Particularly preferably, R stands for C1-C3-alkyl; or forC1-C3-alkyl substituted by at least 1 chlorine atom and/or by at least 1fluorine atom. Very particularly, R stands for CH₃, C₂H₅, CF₃, CF₂Cl,CFCl₂, CCl₃, CHF₂, C₂F₅ or C₃F₇.

R may however also stand for aromatic radicals such as phenyl or tolyl.

The chlorine-fluorine exchange according to the present invention ispreferably performed at a temperature from ambient temperature (about20° C.) to 150° C. Preferably the molar ratio of the HF adduct of thehydrofluoride, relative to the base contained therein, to acid chloridelies in the range from 1:0.01 to 1:1 (1 mole R₃N.2.6 HF and 1 mole acidchloride are then in a ratio of 1:1), if one Cl atom is to be exchangedper acid chloride adduct. In the case of a plurality of chlorine atomswhich are to be exchanged per molecule, the use of the hydrofluoride isexpediently twice, three times, etc. as high. For a continuousprocedure, the ratio may lie in the range from 1:0.01 to 1:100.

Upon the reaction, hydrogen chloride is released spontaneously in thepreparation of carboxylic acid fluorides. This hydrogen chloride can belet off from the reactor (for example by a correspondingly adjustedpressure-relief valve). When preparing SO₂F₂, the addition of acids suchas trifluoroacetic acid is necessary in order to release HCl.

It was established in tests that often the addition of e.g.trifluoroacetic acid right at the beginning of the fluorination reactionis advantageous insofar as the precipitation of solids (whichre-dissolve again later) is prevented or reduced. For example, as littleas 10 mole % of the acid, relative to the onium-HF adduct calculated as100 mole %, is sufficient.

It was also established that ammonium salts having three C1 or C2 alkylradicals very easily release resulting HCl; however, they tend to formsolids, so that the addition of e.g. trifluoroacetic acid, as describedabove, is advantageous. Although onium salts having three C3- orhigher-chain alkyl radicals do not form solids, HCl is not so easilyreleased therefrom as from the shorter-chain substituted onium salts. Inthis case, addition of acid is advantageous, because this expels HClmore intensively.

According to one embodiment, the hydrofluoride adduct functions as afluorination agent. It is then used in such a quantity that it is notdehydrofluorinated to such an extent that the stage of the oniummonohydrofluoride is exceeded. If, for example, an adduct of the formulaR₃N.2.6 HF is used, only such a quantity of HF should be used thatR₃N.zHF with z=1 or z>1 remains in the reaction mixture. Thecorresponding hydrochloride should not be produced if it is desired toavoid regeneration under pressure with HF for as long a time aspossible. It is sufficient here merely to add HF.

If, for example, a chlorine atom is to be exchanged for a fluorine atomin a compound, at least 1 mole of the adduct R₃N.2.6 HF is used per 1.6moles of the starting compound. If other educts (e.g. SO₂Cl₂) or oniumsalts having a different HF content are used, the stoichiometry shouldbe adapted accordingly.

According to another embodiment, the hydrofluoride adduct functions as acatalyst. Then HF is also introduced into the reaction as fluorinationagent. The quantity of HF is then advantageously at least 1 mole HF perchlorine atom to be exchanged. The ratio of the total of free HF and HFbound in the adduct to the chlorine atom to be exchanged may for examplelie in the range from about 1:1 up to 1:3, if SO₂F₂ is to be preparedfrom SO₂Cl₂ or SO₂FCl. In the preparation of carboxylic acid fluoridesor SO₂FCl, it may be still higher if HF is to act as a solvent. It isalso possible to use less than 1 mole HF per chlorine atom to beexchanged; then the HF from the HF adduct which per se has a catalyticeffect is consumed, and the yield drops.

Compared with the known method, the hydrofluoride of ammonia or of theorganic nitrogen base does not function here as a fluorination agent andreaction partner, but as a catalyst. For this reason, a continuousprocedure becomes possible for the first time. The hydrogen chloridereleased may if desired be let off continuously from the reaction systemor be removed upon regeneration. It is not necessary to use a solvent.

Thus the method according to the invention has the advantage thatworking-up is very much easier: no amine hydrochloride is produced aswaste product; and a solvent does not need to be separated off.

A further subject of the invention is a composition which has afluorinating action. It is obtainable by mixing HF adducts of theformula B¹.mHF and an acid. This has the effect of releasing HCl fromthe reaction mixture during the preparation of SO₂F₂. Optionally, baseB¹ may also be added, in a quantity less than the quantity necessary toneutralise the acid. B¹ stands for NH₃ or the base B, as defined above,and m is 1<m<4. The preferred acid is a halogenated carboxylic acid,such as trifluoroacetic acid. The HF adduct of B¹ may also be producedin situ. If desired, this acid or part of the acid may be introduced inthe form of the salt with B¹. The preferred composition has the“formula” B¹.(0.1-1.0)TFA.(1.0-3.0)HF. TFA is trifluoroacetic acid. B¹is preferably B. The preferred B is set forth above.

The use of HF adducts of onium salts of nitrogen as fluorinationcatalyst for the fluorine-chlorine exchange and the fluorine-bromineexchange in carbon atoms activated by additional electronegativesubstituents, in particular in C(O)Cl and C(O)Br groups, is likewise asubject of the invention.

The following examples are intended to explain the invention further,without limiting its scope. Examples 1 to 6 explain the use of HFadducts as fluorination agents (presumably autocatalytically), andExamples 7 to 8 explain the use as a catalyst.

EXAMPLES Example 1

Preparation of Chlorodifluoroacetyl Fluoride (CDFAF) FromChlorodifluoroacetyl Chloride (CDFAC) Using Tributylamine.2.6 HF

ClF₂C—COCl+(CH₃—CH₂—CH₂—CH₂)₃ N.2.6 HF→ClF₂C—COF+HCl

Batch:

0.90 mol chlorodifluoroacetyl chloride (CDFAC) 134.0 g 0.56 moltributylamine.2.6 HF 133.5 g 0.50 mol chlorodifluoroacetic acid 74.5 g

Set-up and Performance:

The tributylamine.2.6 HF was placed in a 250 ml three-necked flask witha reflux condenser, temperature sensor and dropping funnel. The refluxcondenser was fed with cold brine at a temperature of −20° C. via acryomat. After the reflux condenser was located a bubble counter, whichindicated the escape of gaseous products. In order to collect thereaction product, a 300 ml steel cylinder with dip pipe was connectedafter the reflux condenser, the cylinder being kept at a temperature of−78° C. in a Dewar flask with CO₂/methanol.

CDFAC was then dropped into the solution slowly and with vigorousstirring at room temperature. The reaction was slightly exothermic, withthe temperature not increasing to above 31° C. Immediately afterdropwise addition had begun, evolution of gas was observed. The firstsample was taken after the condenser after 15 minutes. Several sampleswere taken during the reaction, and after about two-thirds ofstoichiometry HCl was also detected in the waste gas stream. After onehour, the cryomat was set to −30° C., because too much CDFAC wasescaping. Once the CDFAC had been completely added, stirring wascontinued until the evolution of gas (bubble counter) was at an end.Then the temperature was raised again to 50° C. in order fully to expelthe reaction products in the water bath, until no further escape ofreaction products could be detected at the bubble counter. Then the CDFAwas added in order to expel HCl completely.

Evaluation

The gas samples at the beginning of the reaction had a content of 91%chlorodifluoroacetyl fluoride and 7% entrained chlorodifluoroacetylchloride (% GC surface area) and initially no HCl. Once a total of 0.6mol CDFAC had been introduced dropwise, the resulting HCl was alsoreleased from the reaction solution and confirmed using GC-MS. The steelcylinder contained a mixture of 91.7% CDFAF and 6.9% CDFAC entrainedfrom the reaction, as well as 1.4% HCl (owing to the temperature, whichwas too low for HCl condensation, the resulting HCl was not condensed inthe steel cylinder). The isolated yield of CDFAF and CDFAC was 89.5% oftheory.

Examples of the Preparation of SO₂F₂ from SO₂Cl₂ Using Tributylamine.2.6HF and Tributylamine.TFA.2.6 HF

SO₂Cl₂+2 (CH₃—CH₂—CH₂—CH₂)₃ N.2.6 HF+TFA→SO₂F₂+2 HCl

Example 2

Subsequent addition of TFA to release the HCl

Batch:

0.30 mol sulphuryl chloride (SO₂Cl₂) 40.5 g 0.375 mol tributylamine.2.6HF 71.2 g 0.375 mol trifluoroacetic acid 42.8 g

Set-up and performance from this example also applies to all subsequentexamples:

The tributylamine complex was placed in a 250 ml three-necked flask witha reflux condenser, temperature sensor and dropping funnel. The refluxcondenser was fed with cold brine at a temperature of −30° C. via acryomat. A bubble counter installed after the reflux condenser showedthat products were leaving via the reflux condenser. In order to collectthe reaction product, a steel cylinder (having a volume of approx. 300ml) with dip pipe and gas outlet was connected after the condenser, thecylinder being kept at a temperature of −78° C. in a Dewar flask withCO₂/methanol. SO₂Cl₂ was then dropped into the solution slowly and withvigorous stirring at room temperature. The reaction was slightlyexothermic. A short time after dropwise addition had begun, evolution ofgas was observed, and GC analysis of the gas after the reflux condenserindicated 85.6% SO₂F₂ in addition to 14.3% SO₂FCl (no HCl). At thebeginning of the reaction, the solution in the flask became somewhatdarker in colour, but became light again, and virtually colourless,after some time.

Since hitherto no HCl had been detected in the waste gas (necessary inuse for catalytic fluorination), once the evolution of gas from theabove reaction was at an end (observation of bubble counter),trifluoroacetic acid (TFA) was added carefully dropwise. Immediately,HCl and also further quantities of SO₂F₂ were released from the reactionsolution. In order to complete the expulsion of reaction products andthe reaction, the reaction solution was brought to 50° C. until nofurther evolution of gas was observed at the bubble counter. Theisolated yield in the cylinder was only 48% owing to the inadequatecooling.

Example 3

Experiment with a TFA/NBu₃ ratio of 1:1/Immediate use of Bu₃N/HF/TFA ascatalyst mixture

Batch:

0.23 mol SO₂Cl₂ 31.7 g 0.20 mol tributylamine.2.6 HF 47.5 g 0.123 moltributylamine 22.8 g 0.323 mol trifluoroacetic acid 36.8 g

Set-up:

As for Example 2.

Preparation of the fluorinating composition:

The HF adduct of tributylamine and the tributylamine were mixedtogether. Then the trifluoroacetic acid was added slowly dropwise.

Performance of the fluorination:

The SO₂Cl₂ was added slowly dropwise. HCl and also SO₂F₂ and SO₂FClcould be detected immediately in the waste gas.

Example 4

Test with NBu₃/TFA=1:0.1

Batch:

0.35 mol SO₂Cl₂ 47.2 g 0.30 mol tributylamine.2.6 HF 71.2 g 0.03 moltributylamine 5.6 g 0.03 mol trifluoroacetic acid 3.4 g

Set-up and performance

As for Example 3.

When the first drops of SO₂Cl₂ were added, the waste gas had acomposition of 73.4% SO₂F₂ and 25.1% SO₂FCl, and initially no HCl.Later, the composition changed somewhat in favour of the sulphurylfluoride to 97.2% SO₂F₂ and only 2.0% SO₂FCl and 0.3% HCl. A massbalance was not established.

Example 5

Test with NBu₃/TFA=1:0.23

Batch:

0.35 mol SO₂Cl₂ 47.2 g 0.30 mol tributylamine.2.6 HF 71.2 g 0.09 moltributylamine 16.7 g 0.09 mol trifluoroacetic acid 10.34 g

Set-up and performance:

As for Example 3. In this experiment, a suitable steel cylinder wascooled with liquid nitrogen, in order to obtain a mass balance.

When the first drops of SO₂Cl₂ were added, the waste gas had acomposition of 85.1% SO₂F₂ and 14.8% SO₂FCl and 0.6% HCl. The mixturecondensed in the steel cylinder consisted of 82% SO₂F₂ and 18% SO₂FCland traces of HCl and SO₂. This corresponds to a theoretical yield of90.3%, relative to isolated quantities of SO₂F₂ and SO₂FCl.

Example 6

Preparation of trifluoroacetyl fluoride (TFAF) from trifluoroacetylchloride (TFAC) with tributylamine.2.6 HF as catalyst

Batch:

104.2 g tributylamine.2.6 HF 0.44 mol 151.0 g trifluoroacetyl chloride1.14 mol

Set-up and performance:

The tributylamine.2.6 HF was placed in a 250 ml multi-necked flask withstirrer, temperature sensor and a condenser placed on top (−50° C.) anda bubble counter at the outlet, and TFAC was introduced with stirring atroom temperature.

The reaction became slightly exothermic (T max. 32° C.). Spontaneousevolution of gas occurred. During the reaction, the colour of thesolution changed from light to medium brown. Once the experiment hadended, corrosion of the glass was observed in the bottom.

A sample of the waste gas after the bubble counter contained 88.3% TFAFin addition to TFAC and HCl. A mass balance was not established.

Examples 7 and 8

Experiments for the use of NBu₃.2.6 HF as fluorination catalyst

Example 7

Continuous process using tributylamine.2.6 HF (without TFA) as catalyst

Batch:

0.74 mol sulphuryl chloride (SO₂Cl₂) 100.00 g 0.40 mol tributylamine.2.6HF 94.9 g 0.46 mol 1,1,1,3,3-pentafluorobutane     (S 365mfc) 68.3 g1.48 mol HF 29.6 g

Set-up and performance (applies to the subsequent example):

365 and sulphuryl chloride were placed in a 250 ml PFA washing bottleand were cooled with ice. Then HF was introduced carefully withstirring. The tributylamine complex was placed in a 250 ml three-neckedflask with a reflux condenser, temperature sensor and dropping funnel.The reflux condenser was fed with cold brine at a temperature of −30° C.via a cryomat. The mixture consisting of HF/S365/SO₂Cl₂ was dropped intothe oily, light-brown solution slowly and with vigorous stirring at roomtemperature. The reaction was exothermic (ΔT=22° K.), and the internaltemperature rose to the boiling point of the 365mfc (41° C.). The 365mfcwas retained in the reaction flask by the condenser. A short time afterdropwise addition had begun, evolution of gas was observed; in additionto HCl, SO₂F₂ and mainly SO₂FCl were released. A mass balance was notestablished.

Example 8

Continuous process using tributylamine.2.6 HF with TFA as catalyst

Batch:

0.80 mol sulphuryl chloride (SO₂Cl₂) 107.98 g 0.20 mol tributylamine.2.6HF 47.74 g 1.60 mol HF 32.0 g 0.77 mol S 365mfc 113.3 g 0.02 moltributylamine 3.7 g 0.02 mol trifluoroacetic acid 2.3 g

Set-up and performance:

See above.

A short time after dropwise addition had begun, evolution of gas wasobserved; in addition to HCl, SO₂F₂ and mainly SO₂FCl were released. The365mfc was very largely retained in the reaction flask by the condenser.The evolution of HCl took place somewhat earlier than in the precedingexperiment. A mass balance was not established.

Example 9

Use of NEt₃.2.6 HF as fluorination catalyst for the preparation of SO₂F₂

NEt₃.2.6 HF+SO₂Cl₂→SO₂F₂

Batch:

Substance Molecular weight Weight in g Moles Triethylamine.2.6 HF 153.2258.2 0.38 Sulphuryl chloride 134.97 41.6 0.31

Performance:

Triethylamine.2.6 HF was placed in a three-necked flask with a glasscondenser (˜0° C.) and final bubble counter, and SO₂Cl₂ was addeddropwise with stirring at room temperature. At the beginning of thedropwise addition of SO₂Cl₂, the waste gas leaving the condenser had acomposition of 63% SO₂F₂ in addition to 37% SO₂FCl. Towards the end ofthe reaction, the SO₂F₂ content dropped to 56% SO₂F₂. A mass balance wasnot established.

Example 10

Preparation of SO₂FCl from SO₂Cl₂ using tributylamine.4.5 HF

SO₂Cl₂+(CH₃—CH₂—CH₂—CH₂)₃N.4.5 HF→SO₂FCl+HCl

Batch:

0.24 mol sulphuryl chloride (SO₂Cl₂) 47.2 g 0.24 mol tributylamine.4.5HF 68.4 g

Set-up and performance:

The tributylamine was placed in a 250 ml three-necked flask with areflux condenser, with a bubble counter, temperature sensor and droppingfunnel. The reflux condenser was fed with cold brine at a temperature ofapproximately 0° C. via a cryomat. SO₂Cl₂ was then added dropwise to theoily, light-brown solution slowly and with vigorous stirring at roomtemperature. The reaction was slightly exothermic (ΔT=10° K.). A shorttime after dropwise addition had begun, evolution of gas was observed.As a means of monitoring the reaction, gas chromatography samples weretaken from the waste gas stream after the bubble counter during thedropwise addition. At the beginning of the addition of SO₂Cl₂ the wastegas composition was 55.2% HCl, in addition to 42.07% SO₂FCl; SO₂ wasalso detected. Once dropwise addition of SO₂Cl₂ had ended, the waste gascomposition was virtually identical. A mass balance was not established.

Example 11

Preparation of acetyl fluoride from acetyl chloride withtriethylamine.2.6 HF as catalyst

Batch:

61.3 g triethylamine.2.6 HF 0.40 mol 50.2 g acetyl chloride 0.64 mol

Set-up and performance:

The triethylamine complex was placed in a 250 ml three-necked flask witha reflux condenser, temperature sensor and dropping funnel. The refluxcondenser was fed with cold brine at a temperature of +15° C. via acryomat. Acetyl chloride was added dropwise into the oily, light-brownsolution slowly and with vigorous stirring at room temperature. Thereaction was slightly exothermic, and the evolution of gas took placespontaneously. Once the addition had ended, the solution was heated for1 hour to 80° C., in order to complete the reaction and to drive out anydissolved acetyl fluoride.

Evaluation:

At the beginning of the addition of acetyl chloride, the waste gascomposition was 10.98% HCl, 80.97% acetyl fluoride, 6.59% non-reactedacetyl chloride and 1.46% acetic acid (the latter presumably formed bymoisture present in the sampling cylinder; proportions each given in %GC). Once dropwise addition had ended, the waste gas composition was9.57% HCl, 27.53% acetyl fluoride, 58.01% non-reacted acetyl chlorideand 4.89% acetic acid.

Example 12

Preparation of acetyl fluoride from acetyl chloride withtributylamine.4.0 HF as catalyst

Batch:

79.6 g tributylamine.4.0 HF 0.30 mol 70.7 g acetyl chloride 0.90 mol

Set-up and performance:

The tributylamine complex was placed in a 250 ml three-necked flask witha reflux condenser (and bubble counter), temperature sensor and droppingfunnel. The reflux condenser was fed with cold brine at a temperature of−15° C. via a cryomat. Acetyl chloride was added dropwise into the oily,light-brown solution slowly and with vigorous stirring at roomtemperature. The reaction was slightly exothermic, and the evolution ofgas took place spontaneously. Once the addition had ended, the solutionwas heated for another hour to 80° C., in order to complete the reactionand to drive out any dissolved acetyl fluoride.

Evaluation:

At the beginning of the addition of acetyl chloride, the waste gascomposition was 50.63% HCl, 37.80% acetyl fluoride, 8.15% non-reactedacetyl chloride and 3.43% acetic acid (the latter formed by moisturepresent in the sampling cylinder; proportions each given in % GC). Oncedropwise addition had ended, the waste gas composition was 31.57% HCl,45.96% acetyl fluoride, 19.98% non-reacted acetyl chloride and 2.50%acetic acid.

Examples 11 and 12 prove that acetyl fluoride can also be prepared withadducts having a relatively high HF content.

Examples 13 to 19 explain the regeneration (recycling) of the HF adductcontaminated by HCl.

Example 13

Recycling of NBu₃.1.7 HCl to form NBu₃.Y HF using little HF

Batch:

Substance Molecular weight Weight in g Moles Tributylamine.1.7 HCl247.34 82.17 0.33 HF 20.01 50 2.5

Tributylamine.1.7 HCl was placed in a laboratory autoclave. Afterclosure, 50 g HF was added and the mixture was boiled for approximately3 hours at 100° C. internal reactor temperature. The autoclave was thencooled to approximately 60° C. internal reactor temperature, and the gasphase up to atmospheric pressure in the autoclave was passed into awashing bottle with water.

Determined according to the chloride and fluoride analysis of thewashing bottle, the catalyst remaining in the autoclave then had acomposition of tributylamine.0.62 HCl.7.3 HF.

The example shows that even HF adduct which is completely spent, forminghydrochloride, can be regenerated. The regenerated adduct was able to bere-used in fluorination reactions.

The following example shows that the HCl content of this product can bereduced still further.

Example 14

Further reduction of the HCl content in NBu₃.0.62 HCl.7.3 HF to formNBu₃.Y HF using an excess of HF

Batch:

Weight Substance Molecular weight in g Moles Tributylamine.0.62 HCl.7.3HF 354.3 116.83 0.33 HF 20.01 107 5.35

Another 107 g HF was then added to the mixture from Example 13 oftributylamine.0.62 HCl.7.3 HF remaining in the autoclave, and themixture was boiled overnight at about 100° C. The autoclave was thencooled to approximately 60° C. internal reactor temperature, and the gasphase up to atmospheric pressure in the autoclave was passed into awashing bottle with water. Determined according to the chloride andfluoride analysis of the washing bottle, the catalyst remaining in theautoclave then had a composition of tributylamine.0.005 HCl.4.89 HF.This composition was confirmed by direct analysis of the remainingresidue in the autoclave. The HCl had thus been expelled virtuallycompletely. Decomposition products of the amine were not found.

The resulting composition was excellently usable as a fluorinationreagent and fluorination catalyst.

Example 15

Recycling of NEt₃.1.0 HCl to form NEt₃.Y HF using an excess of HF

Batch:

Substance Molecular weight Weight in g Moles Tributylamine.HCl 137.6537.93 0.28 HF 20.01 107.7 5.38

Performance:

Triethylamine hydrochloride was placed in a laboratory autoclave, whichwas closed. Then HF was added and the mixture was boiled overnight at aninternal reactor temperature of 100° C. Then at 100° C. reactortemperature the gas phase up to atmospheric pressure was let off into awashing bottle filled with water. Determined according to the chlorideand fluoride analysis of the washing bottle, the catalyst remaining inthe autoclave then had a composition of triethylamine.0.09 HCl.5.35 HF.This composition was confirmed by direct analysis of the remainingresidue in the autoclave. The HCl had thus been expelled virtuallycompletely. Decomposition products of the amine were not found.

Example 16

Adjusting the ratio of amine to HF to 2.8 in the catalyst mixture fromExample 15

Performance:

The triethylamine.0.09 HCl.5.35 HF mixture obtained in Experiment 15 waspoured into a PFA bottle with frit and the excess HF was expelled withdry nitrogen. Once the weight of the bottle had remained constant for 30minutes, a vacuum of 10⁻³ mbar was applied for another 10 minutes inorder really to remove all the residual amounts of HF. The catalyst thusobtained, according to chloride, fluoride and amine analysis, then had acomposition of triethylamine.2.8 HF. HCl could no longer be found. Therecyclability of the catalyst was thereby proved.

The adjustment of the amine/HF ratio which was effected reproduced thenucleophilic properties of the adduct. It was then excellently suitableas a reagent for the preparation of SO₂F₂ from SO₂Cl₂.

Example 17 and 18

Variation of the duration of the regeneration

Batch:

Substance Molecular weight Weight in g Moles Tributylamine.HCl 137.6510.00 0.07 HF 20.01 16.5 0.82

Performance:

Triethylamine hydrochloride was placed in a laboratory autoclave, whichwas closed. Then HF was added and the mixture was boiled for 1¼ hours ata reactor temperature of approximately 100° C. (autoclave was pre-heatedfor 15 minutes). After this time, the gas phase, within 15 minutes,while the autoclave stood in a oil bath, was let off and analysed(sample 1). The reactor contents (18.07 g) were poured into a PFA bottleand flushed for 5 minutes with nitrogen (18.02 g), 1.54 g of thissolution was taken and was made up to 1 liter with distilled water andanalysed using a wet chemical process (sample 2).

Cl F TEA [g/l] [g/l] [g/l] Sample 1 1.80 8.49 0.07 Sample 2 0.02 0.800.74 TEA = triethylamine

The analysis data then yielded a catalyst composition of: NEt₃.5.75HF.0.08 HCl

Example 19

Batch:

Substance Molecular weight Weight in g Moles Tributylamine.HCl 137.6510.44 0.08 HF 20.01 21.3 1.06

Performance:

Triethylamine hydrochloride was placed in a laboratory autoclave, whichwas closed. Then HF was added and the mixture was boiled for 30 minutesat a reactor temperature of approximately 100° C. (autoclave waspre-heated for 15 minutes). After this time, the autoclave was removedfrom the oil bath and the gas phase was let off within 15 minutes andanalysed (sample 1). The reactor contents (20.96 g) were poured into aPFA bottle and flushed for 5 minutes with nitrogen (20.64 g), 1.1 g ofthis solution was taken and was made up to 1 liter with distilled waterand analysed using ion chromatography (sample 2).

Cl F TEA [g/l] [g/l] [g/l] Sample 1 2.66 1.89 <0.10 Sample 2 0.02 0.670.42

The analysis data yielded a catalyst composition of: triethylamine.8.48HF.0.14 HCl.

What is claimed is:
 1. A method of producing an acid fluoride from acorresponding acid chloride, the acid fluoride being selected from thegroup consisting of sulfuryl fluoride and sulfuryl chloride fluoride, bycontacting sulfuryl chloride, sulfuryl chloride fluoride, or sulfurdioxide and chlorine to produce sulfuryl fluoride, or by contactingsulfuryl chloride or sulfur dioxide and chlorine to produce sulfurylchloride fluoride with a hydrogen fluoride adduct of ammoniumhydrofluoride or of a hydrofluoride of an organic nitrogen base, withoutthe addition of an HF-binding base or an HF-binding solvent, wherein thehydrogen fluoride adduct serves as a fluorination reagent, and is notdehydrofluorinated beyond the stage of ammonium hydrofluoride or of thehydrofluoride of the organic nitrogen base.
 2. A method according toclaim 1, characterized in that the method is performed continuously. 3.A method according to claim 1, characterized in that sulfuryl fluorideis prepared from sulfuryl chloride or a mixture of sulfur dioxide andchlorine, the molar ratio of amine or ammonia and HF in the reactionmixture being kept above 1:3.
 4. A method according to claim 1 for thepreparation of sulfuryl fluoride with regeneration of the HF adduct,wherein in a first stage sulfuryl chloride and HF are reacted togetherin the presence of the HF adduct which is to be regenerated, withsulfuryl chloride fluoride and regenerated HF adduct being produced, andin a second stage the resulting sulfuryl chloride fluoride is reacted toform sulfuryl fluoride, in the presence of HF adduct, wherein in thesecond stage the molar ratio of amine or ammonia to HF in the reactionmixture is kept above 1:3.
 5. A method according to claim 1,characterized in that the HF adduct of a primary, secondary or tertiaryaliphatic amine hydrofluoride with up to 15 C atoms or of a primary,secondary or tertiary amine hydrofluoride with at least one aromaticradical is used.
 6. A method according to claim 5, characterized in thatthe HF adduct of a hydrofluoride of a secondary or tertiary aliphaticamine having a total of up to 15 C atoms or of a secondary or tertiaryamine with a phenyl group is used.
 7. A method according to claim 6,characterized in that the HF adduct of triethylamine hydrofluoride,tri-n-propylamine hydrofluoride, tri-iso-propylamine hydrofluoride,tri-n-butylamine hydrofluoride, pyridine hydrofluoride, piperidinehydrofluoride or N,N-dimethylamine hydrofluoride is used.
 8. A methodaccording to claim 1, wherein the sulfuryl chloride, sulfuryl chloridefluoride, or sulfur dioxide and chlorine is contacted with said hydrogenfluoride adduct at a temperature from ambient temperature to 150° C. 9.A method according to claim 1, further characterized in that an acid isadded.
 10. A method according to claim 9, wherein the acid is ahalocarboxylic acid.
 11. A method according to claim 9, wherein the acidis trifluoroacetic acid.